Hundreds of planned new sheltered accommodation units have been delayed or scrapped owing to proposed cuts to housing benefit, the BBC has learned.
Several housing associations have said they are no longer financially viable.
The flats, for the elderly or people with learning disabilities, are more expensive to build and run because they provide additional support.
Ministers say they are reviewing the sheltered housing sector "to ensure it works in the best way possible".

Communities Secretary Greg Clark has refused an appeal over a proposal to redevelop a former Oxfordshire police station into sheltered accommodation partly on the grounds the scheme was contrary to the neighbourhood plan.
Specialist developer Churchill Retirement Living wanted to demolish the existing police station at Thame and replace it with 45 sheltered flats. The planning authority South Oxfordshire District Council has refused the project and it was the subject of a recovered appeal. The inspector in charge of the hearing recommended that the appeal should be dismissed.